Cindy M. Meston & Penny Frohlich
The DSM-IV describes gender identity disorder as a persistent and strong cross-gender identification and a persistent unease with ones sex. Gender identity disorder is not diagnosed if these symptoms co-occur with a physical intersex condition. As with the sexual disorders, a diagnosis is only made if the symptoms produce marked distress or impairment. According to the DSM-IV, gender identity disorder can occur in childhood, adolescence, and adulthood. Sexually mature individuals may be heterosexual, homosexual, bisexual, or may feel little sexual attraction to either men or women (American Psychiatric Association, 1994). Gender Identity Disorder is often confused with transvestism (cross-dressing) although the two are distinct.
When biological males and females feel a cross-gender identification, it is termed male-to female transsexualism (MF) and female-to-male transsexualism (FM), respectively. Prevalence estimates suggest that MF transsexualism is more common than FM transsexualism although a few studies have found a 1:1 ratio. Prevalence estimates range from 1:10,000 to 1:100,000 for MF and 1:30,000 to 1:400,000 for FM (Cohen-Kettenis & Gooren, 1999; Zucker & Green, 1992).
Studies examining the biological causes of gender identity disorder have typically examined the effects of prenatal hormones on prenatal brain development. During normal prenatal development, the presence of testosterone leads to the development of external male genitalia and to a male differentiated brain. It is hypothesized that for individuals with gender identity disorder, a discrepancy may exist between prenatal genital differentiation and brain differentiation such that the external genitals develop, for example, as male while the brain develops as female. The evidence to support this hypothesis is mixed. Genetic females exposed to high levels of testosterone in utero (e.g., congenital adrenal hyperplasia), rarely develop gender identity disorder. Similar prenatal exposure to antiandrogenic, androgenic, and estrogenic drugs rarely leads to gender identity disorder in either genetic females or males although some of these individuals display abnormal gender role behavior (Cohen-Kettenis & Gooren, 1999). The strongest evidence to suggest that abnormal prenatal brain differentiation may lead to gender identity disorder comes from a recent study examining hypothalamic brain nuclei in men with gender identity disorder. Zhou et al. (1995) found that the central subdivision of the bed nucleus of the stria terminalis (a region of the hypothalamus) was smaller in MF transsexuals compared to normal males but similar in size to normal females, a difference that was not accounted for by hormone therapy. Sadeghi and Fakhrai (2000) recently reported a case of 18-year old monozygotic female twins requesting gender reassignment surgery. The twins had a childhood history of cross-dressing. Unfortunately they were lost to follow up after the initial evaluation but this case suggests that gender identity disorder may have a genetic component.
Recent studies indicate that, compared to controls, MF transsexuals have more older brothers (but not more older sisters) and a later birth order (Blanchard et al., 1995; Zucker et al., 1997). Conversely, FM transsexuals are more likely to have several younger sisters but not brothers compared to controls (Zucker et al., 1998). The histocompatibility-Y antigen (H-Y antigen), which is responsible for the development of the male testes and brain differentiation, may be implicated in this process for males. With progressive male births, mothers may become immunized to the H-Y antigen, leading to increased production of H-Y antibodies, and a disruption in normal brain differentiation (Blanchard et al., 1998).
Social, parental, or familial factors have been associated with mild gender disturbance. MF transsexuals often report over controlling, rejecting fathers. FM transsexuals often report mothers and fathers who were rejecting and mothers who were over protective. It feasible, however, that these differences may have been the result of abnormal gender development, rather than the cause (Cohen-Kettenis & Gooren, 1999).
Childhood gender identity disorder may, in some cases, predict adult gender identity disorder. Fifty-five feminine boys with gender identity disorder were followed into early adulthood. Five of the feminine boys were diagnosed with gender identity disorder, one as a transvestite, 21 as homosexual, 14 as heterosexual, and 14 that were not rated. This suggests that childhood gender identity disorder reflects a high likelihood of either adult gender identity disorder or homosexuality (Green, 1987).
In cases where gender identity disorder is present, if the individual displays only a mild tendency, displays serious psychopathology, or is not functioning well socially, psychotherapy rather than sex reassignment surgery may be advised. For those with extreme symptoms of gender identity disorder, who are free of from psychopathology, and who are functioning well in society, sex reassignment surgery is still not permitted until the person has lived full time as the preferred gender, often for a period of two years. During this period, candidates may be required to change their name, inform their family, boss, and coworkers, cross-dress full time, and receive hormone treatment. This period is considered to be essential for determining whether surgery is appropriate. The candidates have the opportunity to experience what it is like to live as the other gender and to determine whether they are fully prepared for and fully comprehend the impact of living the remainder of their lives as the other sex (Cohen-Kettenis & Gooren, 1999).
A review of sex reassignment surgery outcome studies suggests that in most cases, surgery resolves the gender identity disorder. Depending on the study, between 71% and 97% of subjects were successfully treated with surgery and less than 1% later took steps to reverse the sex reassignment. Factors that predict a poor outcome include: misdiagnosed transvestism, poor surgery outcome, poor social or work functioning, suicidal tendencies, and sex reassignment surgery late in life. This suggests that the current procedure for determining appropriateness of sex reassignment surgery is effective, when applied strictly (Cohen-Kettenis & Gooren, 1999). Male to female transsexuals who are attracted to men (MF homosexuals) seem to have a better post-surgery outcome compared to MF transsexuals who are attracted to women (MF heterosexuals). MF heterosexuals may have a poorer post-surgery outcome because of the added stigma of becoming homosexual after surgery, and because they typically present for surgery much later in life than MF homosexuals and thus are likely to have more male-role investments (e.g., husband, father). FM transsexuals in general have better post-surgery outcome than MF transsexuals (Cohen-Kettenis & Gooren, 1999)
